The present invention relates to an electromagnetic wave absorber, and particularly to a microwave absorber intended for use in an electron beam accelerator.
In an electron beam accelerator, a high-frequency high-power signal is generated by a klystron and supplied to an acceleration tube where an electron beam is accelerated to near light velocity by the electric field applied within the acceleration tube. It is necessary to absorb excess amounts of energy used for accelerating the electron beam and to discharge the absorbed energy in the form of heat to thereby assure the safety of the device. Further, in the case where a power divider is used, it is necessary to absorb power reflected from a load side to protect the klystron. To this end, it is required to provide a wave absorber at an end portion of the acceleration tube or a branch portion of the power divider to thereby absorb unnecessary electromagnetic waves. As such a wave absorber, conventionally, an indirect cooling type microwave absorber composed of dense silicon carbide has been proposed by the present inventor and disclosed in Japanese Patent Application No. 135205/1982. In this indirect cooling type microwave absorber, however, there is a disadvantage in that the power reflection factor becomes larger as the power is increased, resulting in a gradual deterioration of the absorption characteristic and hence a limitation in the power rating of the absorber.